Organic semi-permeable membranes provided with a plurality of separate longitudinal passageways have several advantages with respect to conventional hollow fibers. In effect, they have a high mechanical strength which notably simplifies problems of handling. Moreover, the speeds of production are accelerated due to the fact that a lesser length of membrane is necessary for the production of a bundle. Finally, the provision of filtration modules is greatly simplified. Such advantages have led to a the development of use of these membranes of which the production techniques or the applications are particularly described in the following patents: DE-A-3 022 313; WO-A-8102750; FR A-2,445,163 and JP 5,982,906. However, known techniques and particularly those described in these patents do not permit mastering in a rational manner all of the parameters of production of these membranes and confering thereon particular predefined structures or mastering in a very precise manner the external dimensions of these membranes as well as their passageways.
The present invention seeks to overcome these deficiencies and has as its principal object to provide a process permitting production of membranes having particularly well defined structures and of which the dimensions, as well as those of their passageways, are precisely defined.